Allow vendor-specific args in WMTS tile requests.
Merge pull request #156 from kwilcox/master

Use URLS as defined in GetCaps for CSW operations.  #154
Add support for TileMatrixSetLimits.
Update test scripts.
Cope with inconsistent WMTS spec.
Re-instate `tilematrixsets` as deprecated.
Merge pull request #158 from rhattersley/wmts-kwargs

Allow vendor-specific args in WMTS tile requests.
Merge pull request #155 from rhattersley/limits

Add support for TileMatrixSetLimits.